Re: TCP data throughput for BCM43362

["Jörg Krause" <joerg.krause@embedded.rocks>]

Hi Franky,

On Fr, 2016-08-05 at 17:56 -0700, Franky Lin wrote:
> On Fri, Aug 5, 2016 at 2:29 PM, Jörg Krause <joerg.krause@embedded.ro
> cks>
> wrote:
> 
> > 
> > 
> > 
> > Am 5. August 2016 23:01:10 MESZ, schrieb Arend Van Spriel <
> > arend.vanspriel@broadcom.com>:
> > > 
> > > Op 5 aug. 2016 22:46 schreef "Jörg Krause"
> > > <joerg.krause@embedded.rocks>:
> > > > 
> > > > 
> > > > Hi,
> > > > 
> > > > I'm using a custom ARM board with an BCM43362 wifi chip from
> > > Broadcom.
> > > > 
> > > > The wifi chip is attached via SDIO to the controller with a
> > > > clock of
> > > > 48MHz. Linux kernel version is 4.7.
> > > > 
> > > > When measuring the network bandwidth with iperf3 I get a
> > > > bandwith of
> > > > only around 5 Mbps. I found a similar thread at the Broadcom
> > > community
> > > > 
> > > > [1] where the test was done with a M4 CPU + BCM43362 and an
> > > > average
> > > > result of 3.3 Mbps.
> > > > 
> > > > Interestingly, a BCM43362 Wi-Fi Dev Kit [2] notes a TCP data
> > > throughput
> > > > 
> > > > greater than 20 Mbps.
> > > > 
> > > > Why is the throughput I measured much lower? Note that I
> > > > measured
> > > > several times with almost no neighbor devices or networks.
> > > > 
> > > > This is a test sample measured with iperf3:
> > > > 
> > > >     $ iperf3 -c 192.168.2.1 -i 1 -t 10
> > > >     Connecting to host 192.168.2.1, port 5201
> > > >     [  4] local 192.168.2.155 port 36442 connected to
> > > > 192.168.2.1
> > > port
> > > > 
> > > >     5201
> > > >     [ ID]
> > > > Interval           Transfer     Bandwidth       Retr  Cwnd
> > > >     [  4]   0.00-1.00   sec   615 KBytes  5.04
> > > > Mbits/sec    0   56.6
> > > >     KBytes
> > > >     [  4]   1.00-2.00   sec   622 KBytes  5.10
> > > > Mbits/sec    0   84.8
> > > >     KBytes
> > > >     [  4]   2.00-3.00   sec   625 KBytes  5.12
> > > > Mbits/sec    0    113
> > > >     KBytes
> > > >     [  4]   3.00-4.00   sec   571 KBytes  4.68
> > > > Mbits/sec    0    140
> > > >     KBytes
> > > >     [  4]   4.00-5.00   sec   594 KBytes  4.87
> > > > Mbits/sec    0    167
> > > >     KBytes
> > > >     [  4]   5.00-6.00   sec   628 KBytes  5.14
> > > > Mbits/sec    0    195
> > > >     KBytes
> > > >     [  4]   6.00-7.00   sec   619 KBytes  5.07
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     [  4]   7.00-8.00   sec   608 KBytes  4.98
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     [  4]   8.00-9.00   sec   602 KBytes  4.93
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     [  4]   9.00-10.00  sec   537 KBytes  4.40
> > > > Mbits/sec    0    202
> > > >     KBytes
> > > >     - - - - - - - - - - - - - - - - - - - - - - - - -
> > > >     [ ID] Interval           Transfer     Bandwidth       Retr
> > > >     [  4]   0.00-10.00  sec  5.88 MBytes  4.93
> > > >     Mbits/sec    0             sender
> > > >     [  4]   0.00-10.00  sec  5.68 MBytes  4.76
> > > >     Mbits/sec                  receiver
> > > 
> > > Not overly familiar with iperf3. Do these lines mean you are
> > > doing
> > > bidirectional test, ie. upstream and downstream at the same time.
> > > Another
> > > thing affecting tput could be power-save.
> > 
> > No, iperf3 does not support bidrectional test. Power-save is turned
> > off.
> > 
> > What does iw link say?

It says:

# iw dev wlan0 link
Connected to xx:xx:xx:xx:xx (on wlan0)
	SSID: xxx
	freq: 2437
	signal: -60 dBm
	tx bitrate: 58.5 MBit/s

	bss flags:	short-preamble short-slot-time
	dtim period:	1
	beacon int:	100

Best regards
Jörg Krause